Needle thread tension device for sewing machines



W I YWESS Oct. 11, 1960 R. E. .JOHNSON 2,955,775

NEEDLE THREAD TENSION DEVICE FOR SEWING MACHINES Filed oct. 25, 1957 INVENTOR. Ralph E Johnson AT TR/VE'Y United States Patent NEEDLE THREAD TENSION DEVICE FOR SEWING MACHINES Ralph Ernest Johnson, Mountainside, NJ., assigner to The Singer Manufacturing Company, Elizabeth, NJ., a corporation of New Jersey Filed Oct. 25, 1957, Ser. No. 692,323

3 Claims. (Cl. 242-150) The present invention relates to sewing machines and particularly to a needle thread tension device for sewing machines.

The United States patent of Chason, No. 2,131,005, illustrates a needle thread tension device that is widely used today. In such a device, the adjusting nut is limited to one revolution by means of a stop -arm on an anchor disc that is locked against turning relative to the supporting stud or arbor and a cooperating lug on the outer spring cover which is in turn adjustably locked to the adjusting nut to provide for varying the range of action of the adjusting nut, by a connection including a pin on the 'adjusting nut and `a plurality of holes in the spring cover.

In some decorative 4stitching a very light tension on the needle thread is required. In a tension device as illus- Vtra-ted in the Chason patent the pin and hole connection is held engaged by the action of the tension spring which biases the spring cover outwardly against the adjusting nut, so when the device is adjusted to a very light tension,

there i-s a tendency for the pin to be dislodged from the.

aperture in the spring cover. When disengaged, there is freedom for relative movement between the adjusting nut and the spring cover, thus disturbing the setting and varying the range of action of the adjusting nut so that when normaltension is restored, the same angular positions as indicated by the indicia on the spring cover, do not represent the same amount of tension.

At the same time, adjustment of the range of action of the adjusting nut initially in manufacture or subsequently Iafter it has been disturbed, is dicult since it -requires moving the spring cover axially against the action of the tension spring to disengage the pin from the hole in Vthe spring cover in which it is seated, and while holding it disengaged, effect the desired adjustment and then seat the pin in the corresponding hole. The available degree of adjustment is, of course, limited by the number of holes in the spring cover in which the pin on the adjusting nut can be seated.

In accordance with the above, it is an object of this invention to provide a needle thread tension device similar to that disclosed in the above noted yChason patent in which the tension adjusting nut is positively locked in adjusted position to the element that limits it to one revolution, thus precluding even :at very light tensions the possibility of accidental relative displacementbetween them that would disturb the original tension settings.

It is also an object of this invention to providev in such a needle thread tension device, Ia construction in which adjustment of the range of action of the adjusting nut is facilitated and has an infinitely line range of adjustment.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preerred embodiment of the invention which is hereinafter Mice set -forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction and advantages of it when Iread in conjunction with the accompanying drawings in which:

Fig. 1 is a sectional View of a needle thread tension device in accordance with this invention mounted upon a sewing machine.

Fig. 2 is -an exploded `perspective view of the elements of the tension device illustrated in Fig. 1.

With reference to the drawings there is illustrated at 1 a fragmentary portion of the wall of a sewing machine frame having a boss 2 on the inside thereof for accommodating a bore or recess 3 extending inwardly from thel front face. 'There is provided a reduced diameter bore4 in the bottom of the recess 3, in which bore 4 the end of a cylindrical arbor 5 is mounted and in which it is adjustably secured by a set screw y6. Within the recess 3, the arbor 5 has an enlarged diameter portion 7 the periphery of which is provided with a plurality of longitudinally extending grooves 8 in a selected one of which is seated and thereby anchored the one end 9 of a check spring 10 -coiled about the arbor and having at the other end a laterally extending -thread engaging U-shaped portion 11 terminating in a loop 12 .that is coiled about the arbor. The usual plate 13 is secured to the face of the wall 1 by a screw 14.

The disclosedy tension device is designed to accommodate two needle threads and is therefore provided with thread-engaging means in the form of three `tension discs 15, 16 and 17 having apertures in the center thereof for mounting them on the arbor 5, the center disc 16 being planar and acting Vas a separator between the oppositely dished outer discs 15 and 17. A guard plate 18 is mounted on the arbor `5 outwardly of the tension discs and has an arm 19 seated in an aperture in the wall 1. The innermost tension disc `15 abuts against the shoulder provided at the outer end of the enlarged por-tion 7 of the arbor 5 and the discs 16 and 17 are resiliently urged against it by the guard plate 18 which is in turn biased inwardly by the usual beehive spring 20 coiled about the arbor 5 and having the outer end thereof formedl with a nger 21 that is seated in a slot 22 extending longitudinally inwardly from the free end of the arbor 5. Disposed between the base or inner end of the spring 20 and the guard plate 18 is an inner spring cover 23 having a cylindrical side wall 2-4 and -a base including ya raised central portion 25 for positioning the base of the spring and having an aperture 26 for receiving the arbor 5. The 'aperture 26 is traversed by a diameter bar 27 that is seated in the slot 22 to hold the cover 23 against turning on the arbor 5.

The outer end of the spring 20 `abuts against an anchor disc 28 having a central aperture 29 for mounting the disc on the arbor 5 and having a diameter bar 30 traversing the aperture 29 and Iseated in the slot 22 forgsecuring the disc against turning on the arbor. The anchor disc 28 has a radially extending stop arm 31 that engages against a lug 32 on the inside of an outer spring cover 33 to limit turning of the cover 33 to one revolution. The cover member 33 comprises a centrally apertured flange or base 34 `and a cylindrical side wall 35 that telescopes with the side Wall 24 of the inner spring cover 23 to enclose the spring 20.

The free end of the arbor 5 is formed with external threads 36 which receives an internally threaded adjusting nut 37. The threads 36 and the cooperating threads on the adjusting nut are multiple, preferably sextuple, having a lead in one revolution equal to desired axial displacement of the adjusting nut. The inner end of theadjusting nut is formed with a ange 38 and the external surface thereof is provided with threads 39 for receiving a clamping nut 40. The outer spring cover 33 is clamping nut in place.

range has been accomplished, the lock-ing sleeve 42 is mounted on the adjusting nut 37 with the base 34 thereof secured between the shoulder dened by the ange 38 and the clamping nut 40 thus locking the cover 33 to the adjustingnut for rotation. i

To lock the clamping nut 4t) to the adjusting nut 37 to prevent accidental displacement thereof, the rnut `40 is provided with a counterbore 41 defining an annular space between the nuts 37 and |40 and in which there is inserted a locking sleeve 42. A set screw 43 is threaded radially through the clamping nut to engage the locking sleeve 42 near the inner end thereof to cock the same between the nuts 37 and `40 into a binding relation and tension setting.

lIn operation, the spring acting at its outer end against the adjusting nut 37, -and'acting at its inner end through the inner spring'cover 23 and guard 18, biases the tension discs 15, 16 and 17 against the shoulder on the arbor 5 at the end of the enlarged portion 7 Vof the arbor 5. Turning the adjusting nut 37 will, of course, eiect displacement of the same axially of the -arbor 5, thereby varying the compression of the spring 20 and the bias imposed on the tension discs. Indicia such as the numerals 45 on the cover 33 and the mark or indicator Y 46 on the cover 23 serves to indicate the setting of the tension within the range of adjustment of the adjusting nut, turning of theadjusting nut being limited to the one revolutionby the stop arm 31 of the anchor disc, 28 yand the cooperating stop lug 32 on the cover 33. The range of axial displacement of theV adjusting nut 37 within this one revolution is determined by the initial setting of the adjusting nut and the position of the stop lug 32 relative' tothe stop arm 31 at the time the clamping nu-t secures the cover 33 to the adjustingv nut.

With the construction as above described, the assembly of the tension and adjustment of the range of axial movelment in one revolution has been substantially simplied. With the elements up to and including the anchor disc 28 assembled on the arbor 5,'the adjusting nut 37 is then threaded onto'the end of the arbors to approximately the desired setting corresponding -to one of the end positions in the range of adjustment of the adjusting nut; for example, that position corresponding to minimum tension.

The, cover member 33 is then placed on the adjusting nut with the stop lug 32 engaged against the stop arm 31 on the side corresponding to'minimum tension. The clampingy nut 40 is thenA threaded onto the adjusting nut 37 to secure the cover 33 relative to the adjusting nut. Any further adjustments of the range of action of the ad- Y justing nut that are desired can be effected simply by turning it to an intermediate position asindicated by the in- 'dicia 45, releasing the clamping nut 4i), turning the cover in the desired direction, and then again securing'the When the desired setting of the of the adjusting nut by the clamping nut 40. Thus,

even with a minimum tension setting there isY no pos- Numerous alterations of the'structure herein disclosed will suggest themselves to those skilled in the art. However, it is -to be understood that the present disclosure relates. to a preferred embodiment of my invention which said arbor, aspring mountedI on said arbor between said Y thread tension discs and saidadjusting nut, a spring cover mounted on said adjusting nut and having a cylindrical sidewall enclosing said spring, means for Ilimiting'turning of said spring cover on said arbor to one revolution, and' means for releasably securing said spring cover to said `adjusting' nut for unitary turning therewith on said arbor and for releasing said spring cover for turn- 'ing on said arbor relatively to said adjusting nut, said means comprising a shoulder formed on said adjusting nut, an inwardly extending flange on said spring cover and seated on said shoulder, external threads formed on saidadjusting nut, a clamping nut threaded on said adjusting nut for clamping said ange against said shoulder, and releasable locking means for securing said clamping nut on said adjusting nut. f

2. A thread tension device in accordance with claim 1 in which said means for limiting turning of said spring cover'on said arbor to one revolution comprisesan anchor disc mounted` on said arbor and keyed to said arbor against turning relatively thereto, said anchor disc having a Vradially extending stop arm, and a stop lug on said spring cover and adapted `to abut against said stop arm upon turning of said spring cover relatively to said anchor disc. f

3. A thread tension device for sewing machines comprising yan arbor, thread-engaging ymeans mounted on said'arbor, an'adjusting nut threaded on said arbor, .a spring mounted on said arbor between said adjusting nut Vand said thread-engaging means, `a member carried by said adjusting nut, means for limiting turning of said member on saidv arbor to one revolution, and means for securing said member to said adjusting nut in adjusted position comprising a shoulder on said adjustingV nut and a `clamping nut threaded on said adjusting nut for clamping said member against said shoulder, and means for locking said clamping nut comprising agsleeve, said clamping nut; and adjusting nutl being formed to provide an annular space therebetween at the free end thereof in which said sleeve is received, and a set screw threaded through said clamping nut and engaging theV periphery of said sleeve adjacent to the one end thereof.

References Cited in the le of this patent UNITED *STATESY PATENTS 686,013. Webster Nov. v5, 1901 1,125,975 Davis et al; Jan. 26, 1915 1,167,823 Huffman etal Ian. 11, 1916 1,534,264 Hanson Apr. 21, 1925 2,131,005 Chason Sept. 20, 1938 

